Copper Plated Pressures
I use Berry's Plated bullets and I know they are loaded between lead and jacketed powder wise. My question is: Can I use the speed obtained compared to a jacketed of the same weight and type to estimate how much I should adjust the powder charge? For example:
Berry 124gr HBRN (TP) 9mm
OAL - 1.150
950fps (measured on my chrono)
Compared to Speer manual #14
124gr Jacketed 9mm
OAL - 1.120
Will these two loads have close to the same pressure developed? Berry's thick plated bullets can be pushed to 1450fps (according to their web site). The Speer manual max load is 4.4gr @ 1059fps. Can I use my chrono and match this speed by upping my charge and still feel safe doing to pressure wise? I know to look for over pressure signs on the fired cases, but I have heard that 9mm pressures spike very rapidly.
The reason behind asking is that I would like to load some test rounds, increasing by .1gr for each set starting at 3.8gr (3.8, 3.9, 4.0, etc) and clock them with my chrono and see which sets I get better groups with. I just want to make sure that I stay on the safe side of the pressure scale.
So back to my original question: Is is safe to use the speed as an indication of pressure when comparing thick plated to jacketed loads?